At the time of the start of the Winter War, Mildh was assigned to LLv 26.

On 23 December, SBs from 24 and 44 SBAP attacked targets in the Vipurri - Laatokka area around 11:00.
44 SBAP suffered heavily during these attacks and SB c/n 14/97 of the regiment HQ was shot by fighters at Äyräpää, and crashed at Heinjoki. The pilot kapitan Ivan Yegorovich Borodin escaped by parachute and became a POW (kapitan Ivan Leontyevich Pratsuk and Nikolay Nikolayevich Dementyev KIA). The task had been to attack an AA battery presumed located at Suursaari (Hogland) in Muolaanjärvi.
The target of 4./44 SBAP was Heinjoki railway station. SBs c/n 18/94 and c/n 4/92 were lost after air combat. The pilot of 18/94, leitenant Ivan Kuzmich Sorokin was taken POW (leitenant Fedor Ignatyevich Bannikov and Valentin Mikhailovich Bessonov KIA) and on the next day the MG-gunner of 4/92, Nikolay Ivanovich Lyakhov was captured (starshiy leitenant Boris Fedorovich Glazov and starshiy leitenant Vasiliy Nikolayevich both KIA).
5./44 SBAP was to bomb a Finnish strongpoint at Oinala (south-west of Muolaanjärvi) with six SBs. Two SBs (c/n 3/136 and c/n 14/72) were shot down at Antrea. The crew in c/n 14/72 (leitenant Mikhail Grigoryevich Zaitsev, starshiy leitenant Nikolay Ivanovich Kapustin and Sergey Pavlovich Kuznetsov) was killed. SB c/n 3/136 was hit by ground fire and by fighters and crashed in no-man's land at Noisniemi. The pilot, starshiy leitenant M. G. Golovanov, was able to reach own lines but shturman starshiy leitenant Aleksandr Gerasimovich Makovenko was killed durring arrest while the MG-gunner Konstantin Ivanovich Drozdetskiy was taken POW in the sector of the Finnish 8th Infantry Division.
It is also possible that a sixth SB from 44 SBAP was shot down with the pilot leitenant Petr Smorodin becoming POW (starshiy leitenant Beloglazov and unknown MG-gunner KIA).
24 SBAP lost two SBs. SB c/n 14/220 "4" of 2./24 SBAP was shot down by ground fire at Ilmatorjunta with the crew KIA (leitenant Aleksey Ivanovich Moskalev, leitenant Mikhail Vasilyevich Korneyev and Fedor Timofeyevich Muravyev). SB c/n 6/220 "8" of 4./24 SBAP force-landed at Bazarevo (Nikulas) after air combat with Nikolay F. Kolosov WIA, leitenant Viktor Nikolayevich Sazonov KIA and PAvel Ivanovich Baskakov KIA.
Between 11:17-12:26 on 23 December, 13 I-16s from 7 IAP led by starshiy leitenant Fedor Shinkarenko (4./7 IAP) flew to cover the SB operations in the Vipurri area. In the region of Kaislahti at an altitude of 2,000m, they saw three SBs that flew to the east-southeast and that twelve enemy aircraft (nine Fokker D.XXIs and three Bulldogs) flew from Noraa east-wards. One enemy flight got behind the tails of the SB flight. Two SBs caught fire, while the third begun to fall down disorderly. Meanwhile Shinkarenko's Eskadrilya tried to overtake the enemy and finally caught them over Pienpero station at 11:40. Seven Fokker D.XXIs were claimed shot down and these were claimed by Shinkarenko, starshiy politruk Gavriil Didenko, leitenant A. D. Bulayev, starshiy leitenant Porfiriy Mikhaylyuk, starshiy leitenant Petr Pokryshev, starshiy leitenant Georgiy Larionov and leitenant Boris Aleksandrovich Grigoryev (all of 4./7 IAP). According to some sources, an unknown pilot also claimed a Bulldog. At Honkaniemi-Pilppula, two of the I-16s were shot down in combat and leitenant Vladimir Vasilyevich Zoltarev (I-16 tip 10 c/n 1021779) and leitenant Grigoryev (unsuccessful parachute jump from I-16 tip 5 c/n 5210836) were both killed.
At 11:50, 13 I-16s from 68 IAP led by batalyonnyy komissar Yakovenko reportedly clashed with four Fokker D.XXIs at Karhusuo. Two Finnish aircraft were claimed shot down, and one pilot escaped by parachute. Finnish troops observed a mid-air collision of two I-16s, but only one parachute. This was starshiy leitenant Iosif Iosifovich Kaval'kov of 3./68 IAP, who parachuted from I-16 "228" at Ylä-Säiniö and was captured by Finnish ground forces at Kangaspelto, Muolaa (Koval'kov had arrived to 68 IAP from 25 IAP). Karchenko reportedly landed his I-16 with 30 hits in the aircraft.
LLv 24 and 26 was heavily involved in the attacks on midday engaging both I-16s from 7 and 68 IAP and SB bombers from 24 and 44 SBAP.
Shortly before 11:00, they clashed with the enemy aircraft beginning with I-16s of which three were claimed shot down in the Muolaanjärvi area. These were claimed by kersantti Lauri Nissinen (LLv 24) in FR-98 (1 and 1 damaged I-16 at 10:40 over Muolaanjärvi), luutnantti Aapo Nieminen (LLv 26) in FR-96 (1 and 1 damaged I-16 over Muolaanjärvi between 10:40-10:55), vänrikki Heikki Ilveskorpi (LLv 24) in FR-117 (1 I-16 over Muolaa at 10:45) and ylikersantti Kelpo Virta (LLv 24) in FR-84 (1 damaged I-16 over Kämärä/Kannas at10:48).
At 10:48, a SB (probably from 44 SBAP) was claimed shot down over Heinjoki by three pilots from LLv 24; luutnantti Jorma Karhunen (FR-112), lentomestari Y. Turkka (FR-83) and lentomestari Viktor Pyötsiä (FR-110). Lentomestari Turkka claimed another SB at 10:50 over Pölläkkälä.
The I-16s from 7 IAP intervened and vänrikki Pekka Kokko (LLv 24) in FR-78 claimed a damaged I-16 over Muolaanjärvi at 10:50. Kersantti Pentti Tilli (LLv 26) in FR-103 claimed an I-16 at 10:55 over Kämärä and a second at 11:10 over Noskuanselkä (both probably from 7 IAP).
Luutnantti Jorma Sarvanto (LLv 24) in FR-97 claimed and SB at 11:08 over Ristseppälä and a second as a probable at 11:15 over Noisniemi (both probably from 44 SBAP).
A Bulldog patrol from LLv 26 led by luutnantti Pentti Tevä took off on an interception mission towards Lake Laatokka (Ladoga). Over Käkisalmi at 11:55, they encountered a formation of 6 to 7 SBs from 24 SBAP, which were bombing from the altitude of 1700 m and 100 meters above clouds. Tevä shot one down and it crashed into the Lake Ladoga confirmed by the coastal units. Lentomestari Mildh dove after the formation but could not gain enough speed until surprisingly one SB passed beneath him. He had an opportunity to fire at the SB for several minutes. The SB received hits and dove steep into a low-lying cloud and Mildh was credited with a damaged aircraft.
Finally, at 12:00, majuri Gustaf Magnusson (LLv 24) in FR-99 claimed a SB (probably from 44 SBAP) over Lempaalanjärvi. He described the combat with the SBs:

Kersantti Kinnunen flying on the left flank observed nine SB planes above Vuoksenranta. I dived after kersantti Kinnunen, who pulled away thinking I was an I-16.
I continued after the formation and caught it at Kiviniemi. I chose as my target the rear-most bomber on the left flank. First I fired in the starboard engine, which started to smoke, thereafter I shot the port engine into fire, when the plane began to descend.
Tactically the enemy unit worked well, e. g. lowering the landing gears simultaneously for speed reduction and the next to the one under attack lowered speed in order to obtain a better position for it's rear gunner.
At 12 o'clock the aircraft hit the ground at Lempaalanjärvi."

Mildh claimed one damaged victory during the war, this one being claimed while flying Bristol Bulldog.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1939
	23/12/39	11:55-12:00	1	SB (a)	Damaged	Bulldog	BU-74	Käkisalmi	LLv 26

Biplane victories:1 damaged.
TOTAL: 1 damaged.
(a) Claimed in combat with SBs from 24 SBAP.

Sources:
Ilmavoitot, osa 2 - Kalevi Keskinen and Kari Stenman, ISBN 952-99432-8-8
Red Stars 7 - Talvisota Ilmassa - The Winter War In the Air - Carl-Fredrik Geust, 2011 Apali Oy, Tampere, ISBN 978-952-5877-04-5
Suomen Ilmavoimat part II – 1928-40 – Kalevi Keskinen and Kari Stenman, 2006, ISBN 952-99743-0-2
Information kindly provided by Tuomo Lukkari and Pentti Perttula.